Make generated warning more prominent and helpful

A number of reviews have been submitted that ignore this warning.  While
we now have 01caf624 which will catch
these violations at CI time, that is arguably already too late, and
developers will have wasted their time.

This commit changes the warning to be multiple lines, with a caps
header, such that it's less likely to be ignored.  It also adds
suggestions on how to proceed.

As a note, this also standardizes privilege registry to use the same
warning as the other files, which it didn't previously.

Tested: Comment changes only, no functional changes.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I3224130dbf581dc962187b2fde4dc98ae26de082